Buggy code:
@ Override public String getRelativePathPrefixToContextRoot ( ) { } @ Override public String getRelativePathPrefixToWicketHandler ( ) { } @ Override public String getURL ( ) { } @ Override public String getQueryString ( ) { } } public static final String METHOD_GET = "get" ; public static final String METHOD_POST = "post" ; private static final short FLAG_SUBMITTED = FLAG_RESERVED1 ; private static final Logger log = LoggerFactory . getLogger ( Form . class ) ; private static final long serialVersionUID = 1L ; private static final String UPLOAD_FAILED_RESOURCE_KEY = "uploadFailed" ; private static final String UPLOAD_TOO_LARGE_RESOURCE_KEY = "uploadTooLarge" ; private IFormSubmittingComponent defaultSubmittingComponent ; private Object formValidators = null ; private String javascriptId ; private Bytes maxSize = null ; private boolean multiPart = false ; public Form ( final String id ) { } public Form ( final String id , IModel < T > model ) { } public void add ( IFormValidator validator ) { } public void remove ( IFormValidator validator ) { } private final int formValidators_indexOf ( IFormValidator validator ) { } private final IFormValidator formValidators_remove ( IFormValidator validator ) { } private final IFormValidator formValidators_remove ( int index ) { } public final void clearInput ( ) { } public final void error ( String error , Map < String , Object > args ) { } public final IFormSubmittingComponent findSubmittingButton ( ) { } public final IFormSubmittingComponent getDefaultButton ( ) { } public final Collection < IFormValidator > getFormValidators ( ) { } public final CharSequence getJsForInterfaceUrl ( CharSequence url ) { } public Bytes getMaxSize ( ) { } public Form < ? > getRootForm ( ) { } public String getValidatorKeyPrefix ( ) { } public final boolean hasError ( ) { } public boolean isRootForm ( ) { } public final boolean isSubmitted ( ) { } @ Override public boolean isVersioned ( ) { } public final void loadPersistentFormComponentValues ( ) { } public final void onFormSubmitted ( ) { } public void process ( IFormSubmittingComponent submittingComponent ) { } @ Deprecated public boolean process ( ) { } private void callOnError ( ) { } private void markFormsSubmitted ( ) { } public void removePersistentFormComponentValues ( final boolean disablePersistence ) { } public final void setDefaultButton ( IFormSubmittingComponent submittingComponent ) { } public void setMaxSize ( final Bytes maxSize ) { } public void setMultiPart ( boolean multiPart ) { } @ Override public final Component setVersioned ( final boolean isVersioned ) { } public final void visitFormComponents ( final FormComponent . IVisitor visitor ) { } public final void visitFormComponentsPostOrder ( final FormComponent . IVisitor visitor ) { } private void visitChildrenInContainingBorder ( final FormComponent . IVisitor visitor ) { } private boolean anyFormComponentError ( ) { } private void dispatchEvent ( final Page page , final String url ) { } private void formValidators_add ( final IFormValidator validator ) { } private IFormValidator formValidators_get ( int index ) { } private int formValidators_size ( ) { } private void inputChanged ( ) { } private void persistFormComponentData ( ) { } protected void appendDefaultButtonField ( final MarkupStream markupStream , final ComponentTag openTag ) { } protected void beforeUpdateFormComponentModels ( ) { } protected void delegateSubmit ( IFormSubmittingComponent submittingComponent ) { } protected final String getHiddenFieldId ( ) { } @ Deprecated protected final String getJavascriptId ( ) { } protected String getMethod ( ) { } @ Override protected boolean getStatelessHint ( ) { } protected IValuePersister getValuePersister ( ) { } private boolean isMultiPart ( ) { } protected boolean handleMultiPart ( ) { } @ Override protected void internalOnModelChanged ( ) { } protected final void markFormComponentsInvalid ( ) { } protected final void markFormComponentsValid ( ) { } private void markNestedFormComponentsValid ( ) { } private void internalMarkFormComponentsValid ( ) { } @ Override protected void onComponentTag ( final ComponentTag tag ) { } @ Override protected void renderPlaceholderTag ( ComponentTag tag , Response response ) { } protected boolean encodeUrlInHiddenFields ( ) { } @ Override protected void onComponentTagBody ( final MarkupStream markupStream , final ComponentTag openTag ) { } protected void writeParamsAsHiddenFields ( String [ ] params , AppendingStringBuffer buffer ) { } private String recode ( String s ) { } @ Override protected void onDetach ( ) { } protected void onError ( ) { } @ Override protected void onRender ( final MarkupStream markupStream ) { } protected void onSubmit ( ) { } protected final void updateFormComponentModels ( ) { } private final void updateNestedFormComponentModels ( ) { } private void internalUpdateFormComponentModels ( ) { FormComponent . visitComponentsPostOrder ( this , new Form . FormModelUpdateVisitor ( this ) ) ; MarkupContainer border = Form . findParent ( Border . class ) ; if ( border != null ) { <START_BUG> FormComponent . visitComponentsPostOrder ( border , new Form . FormModelUpdateVisitor ( null ) ) ; <END_BUG> } } protected final void validate ( ) { } protected void onValidate ( ) { } protected final void validateComponents ( ) { } private boolean isFormComponentVisibleInPage ( FormComponent < ? > fc ) { } protected final void validateFormValidator ( final IFormValidator validator ) { } protected final void validateFormValidators ( ) { } private void validateNestedForms ( ) { } private class FormValidatorRemovedChange extends Change { private static final long serialVersionUID = 1L ; private final IFormValidator removed ; public FormValidatorRemovedChange ( final IFormValidator removed ) { } @ Override public void undo ( ) { } } protected String getInputNamePrefix ( ) { } @ SuppressWarnings ( "unchecked" ) public final IModel < T > getModel ( ) { } public final void setModel ( IModel < T > model ) { } @ SuppressWarnings ( "unchecked" ) public final T getModelObject ( ) { } public final void setModelObject ( T object ) { } public static Form < ? > findForm ( Component component ) { } }

Fix:
FormComponent . visitComponentsPostOrder ( border , new Form . FormModelUpdateVisitor ( this ) ) ;